Tank cleaning compound and method of producing same



for. cleaning, descaling, etc.

United States Patent Office 3,296,143 TANKlCLEANINGtCOMROUND AND METHOD 9 i E1 PRODUCING SAME MarYinwM. Boiko, Morton Grove, 11]., assignor to Tri- Bros. Chemical Corporation, Morton Grove, 111., a corporation of Illinois No Drawing. Filed Nov. 12, 11963, Ser. No. 323,119

Claims. (Cl. 252-87) My invention relates to the art of cleaning and descaling watertanks, and has to do more particularly with My invention is designed for domestic and commercial hot-water heater tanks where the water is intended atleast inwpart for bodily use for bathing or internal consumption.

The. art has long been familiar with a wide variety of industrial compounds and methods eminently satisfactory So far as I am aware, most ifnot all of the descaling materials which have been successfully used are objectionably toxic if applied to a human body or introduced therein as in cookery, etc.

: A major, object of my invention is to produce a composition which is highly etfective for cleaning and descaling a hot-water tank where precipitation of organic and inorganic materials is most likely to occur, reducing the thermal efficiency of the heater. My invention avoids the" introduction .into said tank of any material which would have any appreciable toxic effect on or in the human body.

In briefpoutline, I have conceived of a composition which may safely be handled by any technically inexperienced person, such as the ordinary householder, and ofa particular manner of compounding said material suchthat my improved product will have a long shelf life :without substantial deterioration and may safely be itransported without deterioration. T As a further object or advantage of my invention, I

have evolved an improved product of the character referred ilto ,whichis relatively inexpensive, being compounded from relatively common and inexpensive ingredients, and which, furthermore, may be produced by inexpensive equipment, thus making for low cost to the consumeru:

Various other objects and advantages accruing to my invention will become apparent asthe description proceeds.

It is well known, of course, thatthe characteristic of watery:hardn'ess responsible for most scale deposited on thewalls of. hot water tanks is due primarily to the presencein ground water of varying amounts of alkaline earth salts, primarily salts of calcium and magnesium. Such salts usually, precipitate out of water at elevated temperatures, usually depositing stubbornly onto the side and bottom walls of the containerand known as scale. Various means and methods have been employed for removing ,such deposits after the thermal efficiency of the systemhas been materially reduced, such methods generally involving dissolving of the scale. While these known methodslmay accomplish the desired result, they are,generallvundesirable from the standpoint of toxicity, as noted above.

As any chemist knows, the alkaline earth salts may be dissolved readily by mineral acids. However, such reagents, if used in any effective concentration, are not only.1 toxic in. themselves but, in industrial quality, usually 3,296,143 Patented Jan. 3, 1967 contain excessive amounts of even more toxic impurities such as arsenic, etc.

Thus, many reagents highly suitable for descaling boiler tubes, make-up tanks for steam and hot water systems intended for heating and industrial use, for my purposes are impossible of consideration because of their toxicity, inasmuch as my prime concern is for potability and external body use, as required in domestic and commercialhot water heaters.

As my first problem, therefore, I have sought a reagent which will dissolve scale and which, at the same time, is substantially lacking in toxicity to the human body, internally or externally.

Other problems are incidentally involved. Thus,.. in the reaction of an acid with alkaline earth salts, excessive gas evolution may occur. Hence, use of a strong acid (considered in terms of electrolytic dissociation) I find to be highly undesirable.

My research, accordingly, has been directed toward the selection of a weak acid which lacks toxicity and other undesirable qualities. While numerous weak acids might be named, most of them I have found to be unsuitable for my purpose for one reason or another. For example, certain of the weak organic acids which might otherwise be suitable, such as acetic, have a persistent unpleasant odor in aqueous solution, due primarily to the slowness of their dissociation, rendering them unsuitable for my needs.

Furthermore, I find most desirable a weak acid which, among other characteristics, is available in solid form at room temperatures.

substance, which I refer to as an inhibitor, for protecting the tank walls from the acid at levels where scale is substantially lacking. For this purpose I find most suitable a normally solid water-soluble sugar of a type which is available in inexpensive form. The preferred material is a form of industrial sucrose known in the trade as sanding sugar. In lieu thereof I could substitute dextrose, fructose, or any non-toxic sugar having the properties referred to. Said substance in water will tend to stick to the side walls of the tank, slowly dissolving while protecting the tank from acid action.

I also preferably include, in accordance with my invention, an inert colloidal material which will serve the ,dual purpose of further dividing the particles of acid and also of dispersing finely divided scale material resulting from the acid action to form an easily-removable, thin slurry. As examples of such material I may use, for example, a small proportion of activated charcoal, finely ground graphite or silica gel in discrete particles.

The materials making up my improved treating composition are preferably prepared and compounded according to the following procedure, the proportions being indicated with reference to the complete formula.

Step I Activated charcoal, 0.25 to 5 parts by weight, preferably about 0.3 part.

Anhydrous granular citric acid, 75 to 98 parts, prefen ably about 97.

In accordance with my preferred procedure, the charcoal is added to the citric acid and thoroughly mixed therewith at moderate speed at room temperature and relatively low humidity, to avoid caking, until such constituents are well mixed.

Step II Activated charcoal, 0.25 to 5 ably about 0.3 part.

Sanding sugar, 1 to 15 parts, preferably about 2.0 parts.

These ingredients are likewise mixed together under substantially the same conditions as indicated in Step I.

It is considered highly desirable, in packaging my improved composition for the market that the product resulting from Step I be first introduced into the container, say on a continuous conveyor, and thereafter the product of Step II is introduced thereabove. I have found that by this procedure my improved composition will have a much longer shelf life and will withstand the rigors of shipment much better than other modes of preparation and packaging. Thus, the material will be less likely to cake in the container, but will flow freely therefrom when it is desired to use the material for tank cleaning, as contemplated by my invention.

parts by weight, prefer- Tank treatment It is desirable that all water first be drained from the tank. Preferably, my improved composition is then added to water in approximately the ratio of about one pound of said composition described above to about four gallons of water. This may be done in a separate container, avoiding such thorough mixing as will produce complete solution, and promptly introducing the mixture of water and composition through a funnel into the tank to be cleaned, say, through the relief valve opening. A1- ternatively, a measured quantity of water may be introduced into the tank and the appropriate quantity of treating composition is then introduced into the water within the tank.

Preferably, the mixture of water and treating compound is all-owed to remain in the tank for about an hour at about 160 F., after which the solution is drawn from the tank and it is flushed repeatedly for about 20 minutes to remove loose sediment.

The procedure outlined for tank treatment results in dissolving scale deposits from the side walls and bottom of the tank such as might be expected from the use of hard water in a domestic or commercial water heater; also removed are such magnesium salts as might be deposited by electrolytic action from an over-active magnesium anode rod, which is usually present in modern water heaters.

It will be understood that my invention contemplates substitution in the above example of equivalent materials, with such other changes in the procedure as might be required for stoichiometric proportioning.

Various other changes coming within the spirit of my invention may suggest themselves to those skilled in the art; hence, I do not wish to be limited to the specific em- 4 bodiments described or uses mentioned, but intend the same to be merely exemplary, the scope of my invention being limited only by the appended claims.

I claim:

L A substantially dry, non-toxic tank cleaning composition especially suitable for removing substantially water-insoluble salts from a water heater having an anode rod, which comprises about -98 parts by Weight citric acid in substantially anhydrous form dispersed in about 0.25-5 parts of an inert colloidal material selected from the group consisting of charcoal, graphite and silica gel, as one constituent, and about 1-15 parts of a normally solid non-toxic sugar dispersed in an inert colloidal material as the other constituent.

2. A composition as in claim 1, wherein the citric acid is present in about 75-98 parts by weight dispersed in about 0.255 parts of activated charcoal, as the one constituent, and having about 1-15 parts of sanding sugar dispersed in about 0.25-5 parts of activated charcoal as the other constituent.

3. A composition as in claim 2, wherein the one constituent consists of about 97 parts citric acid dispersed in about 0.3 part charcoal, and the other constituent consists of about 2 parts sanding sugar dispersed in about 0.3 part charcoal.

4. A method of removing deposited substantially insoluble salts from tanks and particularly from water heater tanks having an anode rod, said method comprising introducing into said tank a composition as defined in claim 1 dispersed in water and allowing said dispersion to remain in the tank for a substantial length of time at an elevated temperature, withdrawing the contents of said tank and flushing the latter to remove loose particles.

5. A method of removing deposited substantially insoluble salts from water heater tanks having an anode rod, said method comprising introducing into said tank a composition which comprises citric acid,.sugar and an inert colloidal material, said composition removing and dispersing solids resulting from said magnesium anode rod.

References Cited by the Examiner UNITED STATES PATENTS 1,554,483 9/ 1925 Bailey et al. 1,948,029 2/ 1934 Fisher 252-396 X 2,257,545 9/ 1941 Curtis 252-129 2,994,664 8/1961 Wachter 252-142 X 3,003,899 10/1961 Eberhard et a1. 252142 X FOREIGN PATENTS 211,646 12/ 1957 Australia. 575,054 4/1959 Canada.

11,195 1889 Great Britain. 203,268 9/1923 Great Britain. 896,159 5/ 1962 Great Britain.

LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, ALBERT T. MEYERS,

Examiners.

W. E. SCHULZ, Assistant Examiner. 

1. A SUBSTANTIALLY DRY, NON-TOXIC TANK CLEANING COMPOSITION ESPECIALLY SUITABLE FOR REMOVING SUBSTANTIALLY WATER-INSOLUBLE SALTS FROM A WATER HEATER HAVING AN ANODE ROD, WHICH COMPRISES ABOUT 75-98 PARTS BY WEIGHT CITRIC ACID IN SUBSTANTIALLY ANHYDROUS FROM DISPERSED IN ABOUT 0.25-5 PARTS OF AN INERT COLLOIDAL MATERIAL SELECTED FROM THE GROUP CONSISTING OF CHARCOAL, GRAPHITE AND SILICA GEL, AS ONE CONSTITUENT, AND ABOUT 1-15 PARTS OF A NORMALLY SOILD NON-TOXIC SUGAR DISPERSED IN AN INERT COLLOIDAL MATERIAL AS THE OTHER CONSTITUENT. 